Frost Dates for Casper, WY 82604
Last spring frost May 30 · First fall frost September 19 · 112 frost-free days · USDA Zone 5a
ZIP 82604 has about 27,500 people, the largest of 3 ZIP codes in Casper.
Short season: 112 frost-free days. Spring frost risk spans May 9–June 18 (40 days). Fall frost risk spans September 10–September 29 (19 days).
Frost probability for 82604
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | June 18 | May 30 | May 9 |
| Fall (first frost) | September 10 | September 19 | September 29 |
Dates come from NOAA 1971–2000 freeze probabilities at POWDER RIVER #2 (26.3 km away); the 50% date is the median year.
Frost dates by ZIP code in Casper, WY
| ZIP | Last spring frost (50%) | First fall frost (50%) | Zone |
|---|---|---|---|
| 82604 | May 30 | September 19 | 5a |
| 82601 | May 22 | September 19 | 5a |
| 82609 | May 22 | September 20 | 5a |
Which crops fit a 112-day season in Casper
In Casper (112 frost-free days, a short season), 31 of 56 planner crops fit outright, 15 get two plantings, 7 need an indoor start, 2 don't reliably mature, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Apr 25 | Jun 13–Jun 20 | 70 | head-start: Even planted out Jun 13, the outdoor season is about 10 days short; choose an early variety or grow under cover. | — |
| Pepper | Apr 18 | Jun 13–Jun 20 | 70 | head-start: Even planted out Jun 13, the outdoor season is about 5 days short; choose an early variety or grow under cover. | — |
| Lettuce | Apr 4 | May 2–May 9 | 147 | two-plantings: Plant May 2 and again by Jul 29; both mature before Sep 26. | Jul 29 |
| Carrots | — | May 9–May 16 | 154 | fits: 70 days to maturity, 154 available after May 9. | Jul 18 |
| Cucumber | May 9 | Jun 13–Jun 20 | 84 | fits: 60 days to maturity, 84 available after Jun 13. | Jun 23 |
| Beans | — | Jun 6–Jun 20 | 98 | fits: 60 days to maturity, 98 available after Jun 6. | Jun 30 |
| Peas | — | Apr 4–Jun 13 | 175 | fits: 65 days to maturity, 175 available after Apr 4. | Jul 9 |
| Zucchini | May 16 | Jun 13–Jun 20 | 84 | fits: 55 days to maturity, 84 available after Jun 13. | Jun 28 |
| Onion | Mar 7 | May 2–May 16 | 147 | fits: 100 days to maturity, 147 available after May 2. | — |
| Spinach | — | Apr 4–May 23 | 189 | two-plantings: Plant Apr 4 and again by Aug 17; both mature before Oct 10. | Aug 17 |
| Kale | Mar 21 | May 2–May 16 | 161 | two-plantings: Plant May 2 and again by Aug 2; both mature before Oct 10. | Aug 2 |
| Broccoli | Apr 4 | May 2–May 16 | 147 | fits: 80 days to maturity, 147 available after May 2. | Jun 24 |
| Cabbage | Apr 4 | May 2–May 16 | 161 | fits: 70 days to maturity, 161 available after May 2. | Jul 18 |
| Radish | — | Apr 4–Jun 27 | 175 | two-plantings: Plant Apr 4 and again by Aug 18; both mature before Sep 26. | Aug 18 |
| Beets | — | Apr 4–Jun 27 | 175 | two-plantings: Plant Apr 4 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Potatoes | — | May 16–May 23 | 133 | fits: 90 days to maturity, 133 available after May 16. | — |
| Garlic | — | Sep 19 | 217 | overwinter: Plant Sep 19 to Oct 10; harvest the following summer. | Oct 10 |
| Strawberry | — | Apr 25–Jun 20 | 168 | perennial: A perennial: plant Apr 25; it fruits from the following year and keeps producing for several years. | — |
| Corn | May 2 | Jun 6–Jun 13 | 84 | fits: 75 days to maturity, 84 available after Jun 6. | — |
| Pumpkin | May 16 | Jun 13–Jun 13 | 77 | no-fit: Needs 100 days; Casper has 77 after Jun 13. | — |
| Cauliflower | Apr 18 | May 23–Jun 6 | 126 | fits: 75 days to maturity, 126 available after May 23. | Jun 29 |
| Swiss Chard | Apr 4 | May 16–May 16 | 133 | two-plantings: Plant May 16 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Arugula | — | Apr 4–Jun 27 | 189 | two-plantings: Plant Apr 4 and again by Aug 17; both mature before Oct 10. | Aug 17 |
| Brussel Sprouts | Apr 4 | May 2–May 16 | 161 | fits: 100 days to maturity, 161 available after May 2. | Jun 18 |
| Butternut Squash | May 16 | Jun 13–Jun 20 | 77 | no-fit: Needs 100 days; Casper has 77 after Jun 13. | — |
| Eggplant | Apr 11 | Jun 13–Jun 20 | 70 | fits: 70 days to maturity, 70 available after Jun 13. | — |
| Okra | May 2 | Jun 6–Jun 13 | 91 | fits: 55 days to maturity, 91 available after Jun 6. | Jun 28 |
| Basil | Apr 25 | Jun 20–Jun 20 | 77 | fits: 60 days to maturity, 77 available after Jun 20. | Jun 23 |
| Cilantro | — | May 2–May 23 | 147 | two-plantings: Plant May 2 and again by Jul 24; both mature before Sep 26. | Jul 24 |
| Parsley | Mar 21 | Jun 6–Jun 13 | 112 | fits: 70 days to maturity, 112 available after Jun 6. | Jul 4 |
| Celery | Mar 21 | Jun 6–Jun 20 | 112 | head-start: Even planted out Jun 6, the outdoor season is about 8 days short; choose an early variety or grow under cover. | — |
| Scallions | Mar 21 | May 2–May 16 | 161 | two-plantings: Plant May 2 and again by Jul 28; both mature before Oct 10. | Jul 28 |
| Turnip | — | May 2–May 16 | 161 | two-plantings: Plant May 2 and again by Aug 7; both mature before Oct 10. | Aug 7 |
| Kohlrabi | — | Apr 18–May 2 | 175 | two-plantings: Plant Apr 18 and again by Aug 2; both mature before Oct 10. | Aug 2 |
| Bok Choy | May 2 | May 23–May 30 | 126 | two-plantings: Plant May 23 and again by Jul 29; both mature before Sep 26. | Jul 29 |
| Collards | Mar 21 | May 2–May 16 | 161 | two-plantings: Plant May 2 and again by Jul 28; both mature before Oct 10. | Jul 28 |
| Cantaloupe | May 16 | Jun 13–Jun 20 | 70 | head-start: Even planted out Jun 13, the outdoor season is about 15 days short; choose an early variety or grow under cover. | — |
| Chives | Mar 7 | Jun 6–Jun 13 | 126 | fits: 90 days to maturity, 126 available after Jun 6. | — |
| Dill | — | Apr 4–Jun 27 | 175 | two-plantings: Plant Apr 4 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Oregano | Mar 21 | Jun 6–Jun 13 | 126 | fits: 80 days to maturity, 126 available after Jun 6. | — |
| Rosemary | Mar 7 | Jun 6–Jun 13 | 112 | fits: 80 days to maturity, 112 available after Jun 6. | — |
| Sage | Apr 4 | Jun 6–Jun 13 | 126 | fits: 75 days to maturity, 126 available after Jun 6. | — |
| Thyme | Mar 21 | Jun 6–Jun 13 | 126 | fits: 90 days to maturity, 126 available after Jun 6. | — |
| Calendula | Apr 18 | May 16–May 30 | 133 | two-plantings: Plant May 16 and again by Jul 24; both mature before Sep 26. | Jul 24 |
| Cosmos | May 2 | May 30–Jun 13 | 98 | fits: 60 days to maturity, 98 available after May 30. | Jun 23 |
| Lavender | Mar 7 | May 30–Jun 13 | 133 | fits: 90 days to maturity, 133 available after May 30. | — |
| Marigolds | Apr 18 | May 30–Jun 6 | 98 | fits: 50 days to maturity, 98 available after May 30. | Jul 3 |
| Melons | May 16 | Jun 13–Jun 20 | 70 | head-start: Even planted out Jun 13, the outdoor season is about 15 days short; choose an early variety or grow under cover. | — |
| Mint | — | May 30–Jun 13 | 133 | fits: 90 days to maturity, 133 available after May 30. | — |
| Nasturtiums | May 2 | May 30–Jun 6 | 98 | fits: 55 days to maturity, 98 available after May 30. | Jun 28 |
| Pole Beans | — | Jun 6–Jun 20 | 91 | fits: 65 days to maturity, 91 available after Jun 6. | Jun 18 |
| Spaghetti Squash | May 16 | Jun 13–Jun 20 | 77 | head-start: Even planted out Jun 13, the outdoor season is about 13 days short; choose an early variety or grow under cover. | — |
| Sunflowers | — | May 30–Jun 13 | 98 | fits: 70 days to maturity, 98 available after May 30. | Jun 13 |
| Tomatillos | Apr 4 | Jun 6–Jun 13 | 77 | fits: 75 days to maturity, 77 available after Jun 6. | — |
| Watermelon | May 16 | Jun 6–Jun 13 | 77 | head-start: Even planted out Jun 6, the outdoor season is about 3 days short; choose an early variety or grow under cover. | — |
| Yellow Squash | May 16 | Jun 13–Jun 20 | 84 | fits: 55 days to maturity, 84 available after Jun 13. | Jun 28 |
| Zinnias | May 2 | May 30–Jun 13 | 98 | fits: 60 days to maturity, 98 available after May 30. | Jun 23 |
Month by month in Casper
| Month | What to do |
|---|---|
| January | Plan your garden layout and order seeds. Research varieties suited to your frost dates. |
| February | Start the slowest-growing crops indoors: onions, leeks, and celery (10–12 weeks before last frost). |
| March | Start indoors: Chives (Mar 7), Lavender (Mar 7), Onion (Mar 7), Rosemary (Mar 7), Celery (Mar 21), Collards (Mar 21), +5 more. |
| April | Start indoors: Broccoli (Apr 4), Brussel Sprouts (Apr 4), Cabbage (Apr 4), Lettuce (Apr 4), Sage (Apr 4), Swiss Chard (Apr 4), +8 more. Direct sow from: Arugula (Apr 4), Beets (Apr 4), Dill (Apr 4), Peas (Apr 4), Radish (Apr 4), Spinach (Apr 4), +1 more. Plant: Strawberry (Apr 25). |
| May | Start indoors: Bok Choy (May 2), Corn (May 2), Cosmos (May 2), Nasturtiums (May 2), Okra (May 2), Zinnias (May 2), +9 more. Direct sow from: Cilantro (May 2), Turnip (May 2), Carrots (May 9), Potatoes (May 16), Sunflowers (May 30). Transplant from: Broccoli (May 2), Brussel Sprouts (May 2), Cabbage (May 2), Collards (May 2), Kale (May 2), Lettuce (May 2), +12 more. Last frost around May 30. |
| June | Direct sow from: Beans (Jun 6), Pole Beans (Jun 6). Transplant from: Celery (Jun 6), Chives (Jun 6), Corn (Jun 6), Okra (Jun 6), Oregano (Jun 6), Parsley (Jun 6), +17 more. Last sowing dates: Sunflowers (Jun 13), Brussel Sprouts (Jun 18), Pole Beans (Jun 18), Basil (Jun 23), Cosmos (Jun 23), Cucumber (Jun 23), +8 more. |
| July | Last sowing dates: Marigolds (Jul 3), Parsley (Jul 4), Peas (Jul 9), Cabbage (Jul 18), Carrots (Jul 18), Beets (Jul 19), +8 more. |
| August | Last sowing dates: Kale (Aug 2), Kohlrabi (Aug 2), Turnip (Aug 7), Arugula (Aug 17), Spinach (Aug 17), Radish (Aug 18). |
| September | Direct sow from: Garlic (Sep 19). First frost around September 19. |
| October | Last sowing dates: Garlic (Oct 10). |
| November | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
| December | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
Frequently Asked Questions
What is the last frost date for Casper, WY (ZIP 82604)?
The median last spring frost date for Casper, WY (ZIP code 82604) is around May 30. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area. One year in ten frost ends before May 9; one in ten it runs past June 18.
What is the first fall frost date in Casper, WY?
The median first fall frost date for Casper, WY is around September 19. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses. The first frost arrives around September 10 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Casper, WY?
The frost-free growing season in Casper is about 112 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side. In Casper (112 frost-free days, a short season), 31 of 56 planner crops fit outright, 15 get two plantings, 7 need an indoor start, 2 don't reliably mature, 1 crop is perennial.
What USDA hardiness zone is Casper, WY?
Casper, WY is in USDA hardiness zone 5a (2023 USDA Plant Hardiness Zone Map). Zones come from the average coldest winter temperature, so they tell you which perennials survive the winter; the frost dates on this page tell you when to plant.
When should I start tomatoes indoors in Casper, WY?
Start tomatoes indoors Apr 25 and plant out Jun 13 in Casper. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Casper?
Two: plant May 2 and again by Jul 29; both mature before Sep 26.
When do I plant garlic in Casper?
Sep 19 to Oct 10; it overwinters and is ready the following summer.
Can I grow Celery in Casper?
Yes, with help. Even planted out Jun 6, the outdoor season is about 8 days short; choose an early variety or grow under cover.
Which nearby ZIP has a longer season?
Casper (ZIP 82601) has 120 frost-free days, 8 more than Casper (ZIP 82604). See Casper ZIP 82601 frost dates
Nearby and related
- Frost dates for Casper, WY 82601 (21 mi)
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- When to plant in WY
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